(1) Field of the Invention
The present invention relates to an apparatus for preventing the ingress of water into an underwater gun before, during and after the firing of a projectile and a method for sealing an underwater gun barrel opening.
(2) Description of the Prior Art
Little work has been done on apparatus for keeping water out of a gun barrel because until recently it has not been practical to shoot bullets underwater. Newly proven, supercavitation drag reduction techniques now allow bullets to be fired underwater at high enough speeds to cause damage. Accordingly, there is a need for simple and effective means for sealing underwater gun barrels to preclude the entry of water.
Excluding water from a gun barrel is important to underwater gun operation. If water is allowed to enter the gun barrel before or after firing the gun, the gun will not operate effectively.
The prior art includes various devices relating to underwater guns such as disclosed in U.S. Pat. Nos. 44,631; 367,153; 1,270,988; 3,300,888; 3,616,561; 3,729,853; and 4,821,441. For example, U.S. Pat. No. 44,631 discloses a submarine shot conductor having an India-rubber valve mounted on the open end of the shot barrel. Similarly, U.S. Pat. No. 1,270,988 discloses an underwater gun whereby the gun muzzle is sealed by a pivotally mounted cap portion. U.S. Pat. No. 367,153 discloses a submarine gun and port whereby the port which receives the gun barrel is exposed by means of a sliding gate. Multishot guns for underwater use are disclosed in U.S. Pat. Nos. 4,821,441 and 3,729,853 and 3,616,561. These prior art devices do not provide adequate sealing of the gun barrel to preclude the entry of water and/or are overly complex and not practical underwater guns.
U.S. Pat. No. 3,323,457 to Biehl et al., U.S. Pat. No. 3,453,763 to Barr et al. and U.S. Pat. No. 3,580,172 to Hendricks illustrate some other underwater weapons. Keeping the barrel of the weapon clear of water is important to underwater gun operation because it reduces the energy required to eject the bullet, it increases the muzzle velocities that can be achieved, and it reduces the strength requirements and thus the weight of the barrel.
In the Biehl et al. patent, the underwater weapon comprises a device for launching a projectile. One end of the projectile is covered by a frangible diaphragm. The diaphragm is used to maintain the watertightness of the launcher. In operation, the projectile within the launcher is ejected through the frangible diaphragm. The Barr et al. patent relates to an underwater pistol having a rotatable cylindrical magazine. During operation of this pistol, a projectile is driven through a frangible, and fully removable, sealed front barrel cover. The Hendricks patent also illustrates an underwater weapon in which a projectile resides within a launch tube or barrel having a removable plug affixed at one end to prevent the ingress of water.
Other devices are known in the art to render firearms waterproof. U.S. Pat. No. 3,677,132 to Plenge illustrates a muzzle attachment for the barrel of a firearm. The muzzle attachment includes a device for sealing the muzzle behind a bullet passing therethrough to prevent the escape of expanding gases. This device takes the form of a plurality of polyurethane discs sandwiched between flat metallic washers and spaced apart by ring members. The plugs are x-slotted on both faces thereof for permitting a bullet to pass therethrough without fragmenting or rupturing the element. The disc or plug automatically closes and reseals itself after a bullet has been fired. When the muzzle attachment is threadably engaged with the gun barrel, the weapon is waterproof from the barrel end thereof. U.S. Pat. No. 5,105,571 to Kinchin et al. also relates to a method and apparatus for preventing moisture from entering a firearm. In this patent, lightweight plastic covers are disclosed for use as seals for the openings of a firearm such as the muzzle opening or the magazine well opening. The plastic covers are removable through manual operation. It is also possible to remove the covers by actually firing the weapon.
U.S. Pat. No. 4,848,209 to Almeras discloses sealing a driving apparatus for an underwater device. The apparatus includes a barrel holder, a barrel for guiding a fastener intended to be driven by the gases of a propulsive charge and a percussion system for setting of the charge. The barrel of the device is closed by a closure device made by a material which may be perforated by the projectile disposed inside the tubular element or gun barrel.
U.S. Pat. No. 4,742,775 to Harris illustrates still another approach for sealing an end of an underwater device. In the Harris patent, a sealing compound is used to prevent water from penetrating the casing.
Despite the existence of these devices for sealing the end of underwater weapons and the like, there is still a need for a more efficient approach for preventing the ingress of water into a gun barrel and, in particular, to an approach wherein a series of shots can be fired without water entering the weapon.